Process and apparatus for the production of synthesis gas

ABSTRACT

A process for the production of synthesis gas from a hydrocarbon fuel and steam and/or oxygen gas wherein at least part of any steam requirement is provided by heat exchange against exhaust gas from a gas turbine driving an air separation unit supplying at least part of any oxygen requirement for the synthesis gas production. The process is particularly applicable when the synthesis gas is used to prepare a synfuel by methanol synthesis or a Fischer-Tropsch process.

CROSS REFERENCE TO OTHER APPLICATIONS

This is a divisional application of application Ser. No. 09/965,979filed on Sep. 27, 2001 now U.S. Pat. No. 6,534,551.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a process and apparatus for theproduction of synthesis gas, particularly for but not necessarilylimited to, use in the production of hydrocarbon oils and waxes usingthe Fischer-Tropsch (“F-T”) process or methanol by catalytichydrogenation of carbon monoxide.

BACKGROUND OF THE INVENTION

Natural gas may be found in remote locations both on- and offshore. Itis generally expensive and impractical to transport natural gas from itssource to a distant processing plant. One solution is to convert the gason-site to a valuable and easily transportable product. In this way, thevalue of the natural gas may be increased.

Natural gas may be converted to “synthesis gas” which is a mixture ofcarbon monoxide and hydrogen. Synthesis gas may be converted to a solidor liquid synthetic fuel or “synfuel”. The synfuel has less volume perunit mass (i.e. has a greater density) than the natural gas.Accordingly, it is more economical to transport synfuel than acorresponding amount of natural gas.

One disadvantage of the onsite processing of natural gas is that thespace available for the processing apparatus is often limited. Forexample, in situations where the source of natural gas is offshore, agas rig or a sea vessel is used to support the apparatus for extractingthe natural gas. The processing apparatus required to convert naturalgas into synfuel must be as compact and as lightweight as possiblewithout sacrificing efficiency, productivity or cost-effectiveness. Afurther disadvantage is that the remote locations of the processingplants require that the plants are as self-sufficient as possible in theproduction of power to drive associated apparatus.

Examples of synfuels include high molecular weight hydrocarbon compoundsproduced using the F-T process and methanol produced by the catalytichydrogenation of carbon monoxide, Between 50 and 60% of the total costof an F-T liquid or a methanol plant is in the production of thesynthesis gas. Clearly, if the cost effectiveness of the synthesis gasgeneration process is adversely effected in attempting to overcome thesedisadvantages, the overall processing costs of synfuel production couldbe significantly increased.

There are several methods of producing synthesis gas from natural gas.Three such methods are based on the following processes:

Steam methane reforming (“SMR”) which needs imported carbon dioxide orthe consumption of excess hydrogen to achieve the required 2:1 ratio forthe relative proportions of hydrogen and carbon monoxide in theresultant synthesis gas.

Partial oxidation (“POX”) of natural gas with pure oxygen which achievesa hydrogen to carbon monoxide ratio in the resultant synthesis gas offrom 1.6 to 1.8:1.

Autothermal reforming (“ATR”) which consists of a partial oxidationburner followed by a catalyst bed with a feed of natural gas, steam andoxygen to produce the required 2:1 ratio for the relative proportions ofhydrogen and carbon monoxide in the resultant synthesis gas.

Each of these three processes produces high temperature synthesis gas(SMR 800 to 900° C., POX 1200 to 1400° C. and ATR 900 to 1100° C.). Theexcess heat generated in these processes may be used to generate steamwhich, in turn, can be used in steam turbines to drive air separationsystems, air compressors and other equipment. The excess may also beused in part in a secondary gas heated catalytic reformer (“GHR”). For aPOX/GHR combination, the synthesis gas is typically produced at 500-600°C.

Carbon dioxide and methane are well known to have “greenhouse gas”properties. It is, therefore, desirable that processes for theproduction of F-T liquids and methanol have low emission levels of thesegreenhouse gases and other pollutants, for example, oxides of nitrogen(“NO_(x)”).

It is, therefore, desirable that the processing of natural gas toproduce F-T liquids or methanol using synthesis gas is as efficient interms of yield and capital and running costs as possible with minimalemissions and power wastage. In addition, the plant should be compactand lightweight, particularly if located offshore.

Various attempts have been made to develop processes displaying at leastsome of these desiderata. Attempts to integrate certain steps of thecomponent processes are known to achieve some of these goals. Examplesof such attempts are disclosed in WO-A-0003126 (Fjellhaug et al),WO-A-9832817 (Halmo et al) and WO-A-0009441 (Abbott).

U.S. Pat. No. 4,132,065 (McGann; published 2^(nd) January 1979)discloses a continuous partial oxidation gasification process forproducing synthesis gas. A hydrocarbonaceous fuel such as natural gas isreacted with a free oxygen containing gas, preferably air, optionally inthe presence of a temperature moderator such as steam or water toproduce synthesis gas. A portion of the synthesis gas is combusted inthe presence of compressed air to produce a combustion product gas whichis expanded in a gas turbine. Free oxygen containing gas is provided bya compressor that is driven by at least a portion of the power generatedby the expansion of the combustion product gas in the gas turbine.

It is the primary objective of this invention to improve the efficiencyand lower the capital and operation costs of a synthesis gas generationprocess. A further objective of the invention is to reduce greenhousegas emissions from such a process. The process is to have particularapplication in the production of synfuels.

SUMMARY OF THE INVENTION

It has been found that, by integrating a synthesis gas generationprocess with a gas turbine producing power, at least a portion of whichmay be used to drive a cryogenic air separation unit (“ASU”), processefficiency can be increased and process cost reduced. In addition,greenhouse gas emissions can be reduced and the plant can be made morecompact and lightweight. Further, there is an improvement in the levelof self-sufficiency in respect of power generation.

Hydrocarbon fuel gas is reacted with steam and/or oxygen gas in asynthesis gas generation system to produce a synthesis gas productstream. An oxidant gas is compressed to produce a compressed oxidantgas, at least a portion of which is combusted in the presence ofcombustion fuel gas to produce combustion product gas. The combustionproduct gas is expanded to produce power and expanded combustion productgas. Heat from the expanded combustion product gas is recovered by usingthe expanded combustion product gas to heat steam by heat exchange toproduce heated steam, at least a portion of which is used to provide atleast a portion of any steam requirement for producing the synthesis gasproduct stream in the synthesis gas generation system. Additionally oralternatively, at least a portion of the oxygen gas is provided using anASU that is driven by at least a portion of the power generated by theexpansion of the combustion product gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowsheet describing one embodiment of the process of thepresent invention in combination with an F-T process to producehydrocarbon oils and/or waxes.

DETAILED DESCRIPTION OF THE INVENTION

According to a first aspect of the present invention, there is provideda process for the production of synthesis gas, said process comprising:

reacting hydrocarbon fuel gas with steam and/or oxygen gas in asynthesis gas generation system to produce a synthesis gas productstream;

compressing an oxidant gas to produce a compressed oxidant gas;

combusting combustion fuel gas in the presence of at least a portion ofsaid compressed oxidant gas to produce combustion product gas;

expanding said combustion product gas to produce power and expandedcombustion product gas;

heating a first steam stream by heat exchange against a stream of saidexpanded combustion product gas to produce a heated first steam streamand using at least a portion of said heated first steam stream toprovide at least a portion of the steam for producing the synthesis gasproduct stream in the synthesis gas generation system; and/or

providing at least a portion of the oxygen gas using an ASU that isdriven by at least a portion of the power generated by the expansion ofthe combustion product gas.

Whilst the steps of compressing an oxidant gas, combusting combustionfuel gas in the presence of compressed oxidant gas and expanding theresultant combustion product gas can be carried out in dedicated standalone units, it is preferred that these steps are carried out in a gasturbine system.

The synthesis gas generation system may comprise a POX, an ATR or acatalytic ATR. However, using these reactors alone may resultundesirably in a significant amount of waste heat. Therefore, inpreferred embodiments, the synthesis gas generation system comprises aGHR and the process comprises reforming hydrocarbon fuel gas with steamto produce synthesis gas.

The synthesis gas generation system may comprise a POX and GHR incombination. In these preferred embodiments, the process comprises:

partially oxidizing hydrocarbon fuel gas in the presence of oxygen gasin the POX to produce a first intermediate synthesis gas stream; and

reforming hydrocarbon fuel gas with steam in the GHR to produce a secondintermediate synthesis gas stream and combining said intermediatesynthesis gas streams to produce the synthesis gas product stream.

In these embodiments, the POX/GHR system may generate synthesis gasusing steam from a gas turbine waste heat recovery and steam generationsystem (“HRSG”). The steam from the HRSG provides for the deficiency inheat input to the POX/GHR system. At least a portion of the powergenerated by the gas turbine is used, either directly or indirectly, toprovide the power requirement of the ASU.

The oxidant gas may be selected from oxygen or air. In some embodiments,the oxidant gas is oxygen provided by an ASU although, in preferredembodiments, the oxidant gas is air.

Preferably, the process further comprises:

heating water by heat exchange against the expanded combustion productgas stream to produce a heated second steam stream;

heating an oxygen gas stream by heat exchange against the heated secondsteam stream to produce a heated oxygen gas stream; and

using said heated oxygen gas stream to provide at least a portion of theoxygen gas in the synthesis gas generation system.

The water to be heated to provide the heated second steam stream may bea liquid water stream, a two-phase (liquid-vapor) stream or a steamstream. In preferred processes, the heated second steam stream is aportion of the heated first steam stream.

The HRSG may produce excess steam. Introduction of this excess steaminto the combustion of the combustion fuel gas conditions the fuel gaswhich has the effect of increasing the power output of the gas turbine.The process may, therefore, further comprise:

heating water by heat exchange against the expanded combustion productgas stream to produce a heated third steam stream; and

introducing the heated third steam stream into the combustion of thecombustion fuel gas.

The water to be heated to provide the heated third steam stream may be aliquid water stream, a two-phase (liquid-vapor) stream or a steamstream. In preferred embodiments, the heated third steam stream is anexcess portion of the heated first steam stream. The introduction of theexcess steam in this way further integrates the overall process.

An efficient process is one that is balanced, that is to say, a processin which there is no heat or material loss. In the present invention,the excess portion of the heated first steam stream is surprisingly low,i.e. about 3-wt %. The low level of excess steam was unexpected andindicates that the process is substantially balanced. This is asignificant advantage over the known processes.

In preferred embodiments, the hydrocarbon fuel gas comprises methane,natural gas, gas associated with oil production or combustible off-gasesfrom downstream processes and the combustion fuel gas compriseshydrogen, methane, natural gas, gas associated with oil production orcombustible off-gases from downstream processes. The use of natural gasas the hydrocarbon fuel gas and the combustion fuel gas is particularlypreferred. The natural gas should be desulphurized if it is to come incontact with a solid catalyst.

In preferred embodiments, the combustion fuel gas comprisessubstantially pure hydrogen produced from the synthesis gas productstream. The use of hydrogen gas as the sole combustion fuel gas in thisway virtually eliminates all carbon dioxide emissions from the process.This is a further significant advantage of the present invention overthe prior art.

NO_(x) may be produced during the combustion of the combustion fuel gas.If released into the atmosphere, NO_(x) would act as a pollutant. Thelevel of NO_(x) emissions is reduced as the proportion of nitrogenpresent in the combustion is increased. In addition, the combustion fuelgas may be conditioned by introducing compressed nitrogen into thecombustion. This has the effect of increasing the power output of thegas turbine due to the increase in mass of the exhaust gases. Therefore,the process may further comprise:

heating a compressed nitrogen stream by heat exchange against theexpanded combustion product gas stream to provide a heated compressednitrogen stream; and

introducing said heated compressed nitrogen stream into the combustionof the combustion fuel gas.

Preferably, the compressed nitrogen stream is produced by compressing astream of nitrogen produced in an ASU. This step further integrates theoverall process.

In preferred embodiments, the expansion of the combustion product gaswill produce more power than required to drive the ASU. Instead ofallowing a remaining portion of the power generated to be wasted, atleast a part of the remaining portion of the power generated may be usedto provide auxiliary power for downstream processes.

Once the synthesis gas product stream has been produced, it may be usedin a number of ways. In preferred embodiments of the present process,the synthesis gas product stream or a stream derived therefrom isprocessed in a synfuel generation system to produce a synfuel.

Preferably, the synfuel generation system comprises an F-T reactor andthe synfuel is a mixture of high molecular weight hydrocarbon compounds.

The F-T reaction is a catalyzed reaction between carbon monoxide andhydrogen to produce a mixture of high and low molecular weighthydrocarbon compounds, carbon dioxide and water. The expression “highmolecular weight hydrocarbon compounds” includes hydrocarbon compoundshaving at least 6 carbon atoms that are readily condensable to form oilsor waxes. The expression “low molecular weight hydrocarbon compounds”includes gaseous C₁-C₅ hydrocarbon compounds that are not so readilycondensable as the high molecular weight hydrocarbon compounds. At leastportion of combustible off-gases generated in the F-T reactorcomprising, for example, these low molecular weight hydrocarbons may beintroduced as fuel into the combustion of the combustion fuel gas.Alternatively, a stream of at least a portion of the combustibleoff-gases generated in the F-T reactor or a stream derived therefrom maybe combined with hydrocarbon fuel gas to produce a combined gas stream.The combined gas stream or a stream derived therefrom may be fed as fuelto the synthesis gas generation system.

The F-T reaction is highly exothermic and may be expressed by thefollowing reaction scheme:

CO+H₂→—CH₂—+H₂O ΔH=−36.1 kcal/mol@25° C.

The overall efficiency of the process is improved by preheating the feedstreams to the gas turbine and the synthesis gas generation system byheat exchange against either the expanded combustion product gas streamor the synthesis gas product stream in the usual way.

Methanol may be produced by the catalytic exothermic hydrogenation ofcarbon monoxide according to the following reaction scheme:

CO+2H₂→CH₃OH ΔH=−49.43 kcal/mol@25° C.

To produce methanol, the synfuel generation system may comprise areactor provided with a carbon monoxide hydrogenation catalyst. Thesynthesis gas product stream (or a stream derived therefrom) may,therefore, be reacted in a reactor provided with a hydrogenationcatalyst to produce heat and a methanol product stream. Hydrogen,nitrogen and argon may be vented from the reactor.

The methanol product stream may comprise unreacted synthesis gas inwhich case the process may further comprise recycling the methanolproduct stream around the reactor until substantially all of theunreacted synthesis gas has been reacted.

In order to reduce emissions, originating from the methanol generationreactor, into the atmosphere, the process may further comprise:

removing a purge gas stream comprising unreacted synthesis and inert gasfrom the reactor; and

introducing at least a portion of said purge gas stream or a streamderived therefrom as fuel into the combustion of the combustion fuelgas.

At least a portion of the purge gas stream may be recycled by feeding tothe synthesis gas generation system.

In any one of the methanol production processes, heat may be removedfrom the methanol generation reactor by heat exchange with water,preferably to form medium pressure steam.

According to a second aspect of the present invention, there is providedapparatus for the production of synthesis gas according to the processof the first aspect of the present invention, said apparatus comprising:

a synthesis gas generation system for reacting hydrocarbon fuel gas withsteam and/or oxygen gas to produce a synthesis gas product stream;

compressing means for compressing an oxidant gas to produce compressedoxidant gas;

combusting means for combusting combustion fuel gas in the presence ofat least a portion of said compressed oxidant gas to produce combustionproduct gas;

expanding means for expanding said combustion product gas to producepower and expanded combustion product gas;

heat exchange means for heating a first steam stream against a stream ofexpanded combustion product gas to produce a heated first steam stream;

conduit means for supplying the stream of expanded combustion productgas from the expanding means to the first heat exchange means;

conduit means for supplying at least a portion of the heated first steamstream from the first heat exchange means to the synthesis gasgeneration system; and/or

an ASU;

means for transferring at least a portion of the power produced by theexpanding means to the ASU; and

conduit means for supplying at least a portion of the oxygen gas fromthe ASU to the synthesis gas generation system.

Preferably, the apparatus is adapted to carry out any combination of theoptional features of the process described above. In particularlypreferred embodiments, the compressing means, the combusting means andthe expanding means are stages of a gas turbine.

EXAMPLE

The detailed configuration of the process depicted in FIG. 1 depends onthe downstream gas to liquids process and, in particular, the ratio ofhydrogen to carbon monoxide, the amount of carbon dioxide that can betolerated and the amount and composition of the by-products generated.

Referring to the FIG. 1, a natural gas stream 1, pressurized to about 34atm. (3.4 MPa), is divided into a first portion 3 and a second portion2. The first portion 3 is heated to about 300° C. by heat exchangeagainst a hydrogen-enriched synthesis gas product stream 11 in a firstheat exchanger X3 and is then fed to the POX R1 where it is reacted withoxygen. The second portion 3 is combined with a compressed uncondensedby-product stream 24 and fed to the GHR.

A stream 28 of oxygen is heated to about 270° C. in a second heatexchanger X1 against a stream of steam 39, pressurized to about 34 atm.(3.4 MPa) to produce a heated oxygen stream 29 and a cooled steam stream40. The heated oxygen stream 29 is fed to the POX R1 and reacted withnatural gas to produce a first intermediate synthesis gas. A stream 5 ofthe first intermediate synthesis gas leaves the POX at about 1305° C.and enters the shell-side of the GHR R2 where it is mixed with reformedgas exiting the open-ended reformer tubes. The gaseous mixture flows upthe side of the tubes, providing heat for the reforming being carriedout in the tubes, and exits the GHR as a synthesis gas product stream 6.

The synthesis gas product stream 6 leaves the GHR at about 500° C. andis cooled in a third heat exchanger X2 against, inter alia, a portion 33of the steam, pressurized to about 35 atm. (3.5 MPa), required toproduce the desired steam to carbon ratio of about 4:1 in the GHR. Thisstep produces a cooled synthesis gas product stream 7.

The ratio of hydrogen to carbon monoxide in the synthesis gas productstream 6 is about 1.65:1. However, this ratio may not be appropriate forcertain downstream processes. For the present embodiment where thesynthesis gas generated is to be used in an F-T process, a higher ratioof between 1.9 to 2.3:1 is required. In this embodiment, the cooledsynthesis gas product stream 7 is divided into a first portion 8 and asecond portion 9. The second portion 9 is fed to a high temperatureshift reactor (“HTS”) R3 to shift some of the carbon monoxide tohydrogen. The resultant intermediate hydrogen-enriched synthesis gasstream 10 is combined with the first portion 8 that bypassed the HTS toproduce the hydrogen-enriched synthesis gas stream 11 with the requiredratio of hydrogen and carbon monoxide.

The hydrogen-enriched synthesis gas stream 11 is then cooled in thefirst heat exchanger X3 against the vaporisation of a water stream 30,pressurized to 35 atm. (3.5 MPa) and the heating of the natural gasstream 3. This exchange of heat produces the heated natural gas stream 4and a first steam stream 34 and a cooled hydrogen-enriched synthesis gasproduct stream 12.

The first steam stream 34 is further heated to about 430° C. in a fourthheat exchanger X7 located in the HRSG to produce a heated first steamstream 35. A first portion 36 of this stream is combined with the gas tobe reformed in the GHR and a part 39 of a second portion 37 of thisstream is used to pre-heat the oxygen stream 28 in the second heatexchanger X1. An excess part 38, amounting to approximately 3% by weightof the heated first steam stream 35, may be added to a combustor R5.

The cooled hydrogen-enriched synthesis gas product stream 12 is furthercooled in a first condenser X4, thereby condensing steam contaminants inthe synthesis gas and producing a wet synthesis gas stream 13. Water isseparated from the synthesis gas stream in a separator vessel C1 toproduce a first water by-product stream 52 and a water-depletedsynthesis gas stream 14. The water-depleted synthesis gas stream 14 isthen heated to a reaction temperature of about 240° C. in heat exchangerX5 and is fed as stream 15 to the F-T reactor R4 to produce a firsthydrocarbon product stream 16.

A very simplified F-T reactor is shown in the flowsheet. The actual unitwould be far more complex with more than one reactor, unreacted feedrecycle and downstream processing to produce the different cuts of fuelrequired. For this embodiment of the invention, the first hydrocarbonproduct stream produced contains about 64% by weight carbon dioxide.This is based on an F-T reactor system which operates at 28 atm. (2.8MPa) and converts about 92% of the inlet carbon monoxide to hydrocarboncompounds using a cobalt-based catalyst.

High molecular weight hydrocarbon compounds and steam contaminants infirst hydrocarbon product stream 16 are condensed in a third condenserX6. The condensed components in stream 17 are removed from the gaseousby-products in a second separator C2 to produce a wet condensedhydrocarbon product stream 18 and an uncondensed by-product stream 21.The water is removed from the wet condensed hydrocarbon product stream18 in a third separator C3 to produce a second water by-product stream20 and a second hydrocarbon product stream 19 containing the highmolecular weight hydrocarbon products.

A portion 22 of the uncondensed by-product stream 21 is vented toprevent the build up of inert gases such as nitrogen and argon. Thisportion can be added to the combustion fuel gas for the gas turbinecombustor R5. The remaining portion 23 is compressed in a compressor K3to about 32 atm. (3.2 MPa) and combined with natural gas 2 and thecombined stream 25 is heated to about 430° C. in the third heatexchanger X2 to produce a heated steam stream 26 that is combined withsteam to produce the GHR feed stream 27.

The remaining part of the flowsheet concerns the gas turbine and theHRSG. A feed air stream 45 is compressed in a second compressor K1 toabout 12 atm. (1.2 MPa) and a portion 46 is then fed to the combustor R5where it is used to combust natural gas. A stream 47 of combustionproduct gas is expanded, together with the remaining portion 51 of thecompressed air, in an expander K2 to produce an expanded combustionproduct gas stream 48. The waste heat in the expanded gas stream 48 isrecovered in the HRSG against feed streams to the combustor and thePOX/GHR system thereby producing cooled stream 49.

A natural gas stream 41 is heated in the HRSG to produce a heatednatural gas stream 42 that is fed to the combustor R5. A nitrogen stream43 is heated in the HRSG and the resultant heated nitrogen stream 44used to condition the heated natural gas stream 42 in the combustor R5.A second feed water stream 32 is heated in the HRSG to produce theheated water stream 33 that is fed to the third heat exchanger X2 whereit is vaporized to produce a second steam stream that is added to theGHR as feed stream 27.

The power generated by the gas turbine under iso-conditions is 93 MWwhich is enough to provide the power for the ASU (57 MW) and a largepart of the power required for the downstream processes.

The heat and material balance for the exemplified process is provided inthe following Table 1:

TABLE 1 Heat and Material Balance for FT production example underiso-conditions Mole Fraction 1 2 3 4 5 6 7 8 9 10 11 12 13 Oxygen 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Methane 86.08% 86.08% 86.08% 86.08% 0.24% 0.39% 0.39% 0.39% 0.39% 0.39%0.39% 0.39% 0.39% Carbon monoxide 0.00% 0.00% 0.00% 0.00% 33.83% 23.45%23.45% 23.45% 23.45% 11.46% 19.47% 19.47% 19.47% Hydrogen 0.00% 0.00%0.00% 0.00% 57.15% 37.70% 37.70% 37.70% 37.70% 49.69% 41.67% 41.67%41.67% Carbon Dioxide 1.61% 1.61% 1.61% 1.61% 1.38% 11.96% 11.96% 11.96%11.96% 23.94% 15.93% 15.93% 15.93% Water 0.00% 0.00% 0.00% 0.00% 7.13%25.25% 25.25% 25.25% 25.25% 13.26% 21.28% 21.28% 21.28% Argon 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%FT Liquid 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% Ethane 8.02% 8.02% 8.02% 8.02% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Propane 2.66% 2.66% 2.66% 2.66% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Butane 0.57% 0.57% 0.57%0.57% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Pentane0.09% 0.09% 0.09% 0.09% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% Isobutane 0.29% 0.29% 0.29% 0.29% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 2-Methyl-Butane 0.10% 0.10% 0.10% 0.10% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Hexane 0.05% 0.05% 0.05%0.05% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Heptane0.01% 0.01% 0.01% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% Nitrogen 0.52% 0.52% 0.52% 0.52% 0.27% 1.26% 1.26% 1.26% 1.26%1.26% 1.26% 1.26% 1.26% Total Flow KMOL/H 8585 1200 7385 7385 2426254943 54943 36729 18214 18214 54943 54943 54943 Temperature ° C. 25 2525 300 1305 500 313 313 313 443 357 174 40 Pressure BAR 34 34 34 34 3432 32 32 32 32 32 32 32 Pressure MPa 3.4 3.4 3.4 3.4 3.4 3.2 3.2 3.2 3.23.2 3.2 3.2 3.2 Vapor Fraction 1 1 1 1 1 1 1 1 1 1 1 1 0.79 EnthalpyJ/KMOL −8.27E+07 −8.27E+07 −8.27E+07 −6.90E+07 −1.94E+07 −1.19E+08−1.25E+08 −1.25E+08 −1.25E+08 −1.25E+08 −1.25E+08 −1.31E+08 −1.45E+08Average MW 18.94 18.94 18.94 18.94 12.63 17.55 17.55 17.55 17.55 17.5517.55 17.55 17.55 Mole Fraction 14 15 16 17 18 19 20 21 22 23 24 25 26Oxygen 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% Methane 0.49% 0.49% 2.93% 2.93% 0.05% 0.80% 0.00% 5.13%5.13% 5.13% 5.13% 12.38% 12.38% Carbon monoxide 24.68% 24.68% 3.58%3.58% 0.02% 0.31% 0.00% 6.30% 6.30% 6.30% 6.30% 5.73% 5.73% Hydrogen52.83% 52.83% 10.07% 10.07% 0.03% 0.41% 0.01% 17.76% 17.76% 17.76%17.76% 16.17% 16.17% Carbon Dioxide 20.13% 20.13% 37.02% 37.02% 1.31%13.16% 0.49% 64.34% 64.34% 64.34% 64.34% 58.72% 58.72% Water 0.27% 0.27%40.52% 40.52% 93.05% 0.23% 99.50% 0.33% 0.33% 0.33% 0.33% 0.30% 0.30%Argon 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% FT Liquid 0.00% 0.00% 2.25% 2.25% 5.18% 79.79% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Ethane 0.00% 0.00% 0.19% 0.19% 0.01% 0.22%0.00% 0.32% 0.32% 0.32% 0.32% 1.01% 1.01% Propane 0.00% 0.00% 0.19%0.19% 0.04% 0.59% 0.00% 0.30% 0.30% 0.30% 0.30% 0.51% 0.51% Butane 0.00%0.00% 0.18% 0.18% 0.09% 1.43% 0.00% 0.25% 0.25% 0.25% 0.25% 0.28% 0.28%Pentane 0.00% 0.00% 0.18% 0.18% 0.18% 2.84% 0.00% 0.18% 0.18% 0.18%0.18% 0.18% 0.18% Isobutane 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.03% 0.03% 2-Methyl-Butane 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.01% Hexane 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Heptane 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% Nitrogen 1.60% 1.60% 2.89% 2.89% 0.02% 0.23% 0.00%5.09% 5.09% 5.09% 5.09% 4.68% 4.68% Total Flow KMOL/H 43337 43337 2393123921 10388 674 9694 13553 1355 12198 12198 13398 13398 Temperature ° C.40 240 250 40 40 42 42 40 40 40 52 49 430 Pressure BAR 32 32 28 28 28 2828 28 28 28 32 32 32 Pressure MPa 3.2 3.2 2.8 2.8 2.8 2.8 2.8 2.8 2.82.8 3.2 3.2 3.2 Vapor Fraction 1 1 1 0.57 0 0 0 1 1 1 1 1 1 EnthalpyJ/KMOL −1.07E+08 −1.01E+08 −2.49E+08 −2.78E+08 −2.94E+08 −4.19E+08−2.85E+08 −2.66E+08 −2.66E+08 −2.66E+08 −2.66E+08 −2.49E+08 −2.33E+08Average MW 17.41 17.41 31.54 31.54 29.31 190.01 18.14 33.25 33.25 33.2533.25 31.97 31.97 Mole Fraction 27 28 29 30 31 32 33 34 35 36 37 38 39Oxygen 0.00% 99.50% 99.50% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% Methane 8.35% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Carbon monoxide 2.94% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Hydrogen8.29% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% Carbon Dioxide 30.10% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Water 48.90% 0.00% 0.00% 100.00% 100.00%100.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00% Argon0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% FT Liquid 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% Ethane 0.52% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Propane 0.28% 0.00% 0.00% 0.00% 000% 0.00% 0.00% 0 00% 0.00% 0.00% 0.00% 0.00% 0.00% Butane 0.14% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Pentane 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% Isobutane 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 2-Methyl-Butane 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Hexane 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Heptane 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% Nitrogen 2.40% 0.50% 0.50% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Total Flow KMOL/H 26138 5212 52124545 2572 9432 2572 4545 11405 3309 1236 304 932 Temperature ° C. 426 25270 25 430 25 100 340 430 430 430 430 430 Pressure BAR 32 34 34 35 35 3535 35 35 35 35 35 35 Pressure MPa 3.2 3.4 3.4 3.5 3.5 3.5 3.5 3.5 3.53.5 3.5 3.5 3.5 Vapor Fraction 1 1 1 0 1 0 0 1 1 1 1 1 1 Enthalpy J/KMOL−2.31E+08 −2.99E+08 7.38E+08 −2.86E+08 −2.29E+08 −2.86E+08 −2.80E+08−2.32E+08 −2.29E+08 −2.29E+08 −2.29E+08 −2.29E+08 −2.29E+08 Average MW25 31.98 31.98 18.02 18.02 18.02 18.02 18.02 18.02 18.02 18.02 18.0218.02 Mole Fraction 40 41 42 43 44 45 46 47 48 49 50 51 52 Oxygen 0.00%0.00% 0.00% 1.00% 1.00% 21.50% 21.50% 11.94% 12.77% 12.77% 0.00% 21.50%0.00% Methane 0.00% 86.08% 86.08% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% Carbon monoxide 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.01% Hydrogen 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.02% 0.00% 0.02% CarbonDioxide 0.00% 1.61% 1.61% 0.00% 0.00% 0.00% 0.00% 3.41% 3.11% 3.11%0.26% 0.00% 0.26% Water 100.00% 0.00% 0.00% 0.00% 0.00% 1.50% 1.50%7.50% 6.98% 6.98% 99.70% 1.50% 99.70% Argon 0.00% 0.00% 0.00% 0.00%0.00% 1.00% 1.00% 0.85% 0.86% 0.86% 0.00% 1.00% 0.00% FT Liquid 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Ethane 0.00% 8.02% 8.02% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% Propane 0.00% 2.66% 2.66% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Butane 0.00% 0.57% 0.57% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Pentane 0.00% 0.09% 0.09%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Isobutane0.00% 0.29% 0.29% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 2-Methyl-Butane 0.00% 0.10% 0.10% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Hexane 0.00% 0.05% 0.05% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Heptane 0.00% 0.01% 0.01%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Nitrogen0.00% 0.52% 0.52% 99.00% 99.00% 76.00% 76.00% 76.30% 76.28% 76.28% 0.00%76.00% 0.00% Total Flow KMOL/H 932 943 943 3784 3784 30465 27419 3222535272 35272 11606 3047 11606 Temperature ° C. 210.45 25 450 25 450 25360 1133 549 100 40 360 40 Pressure BAR 35 22.4 22.4 22.4 22.4 1.0111.95 11.47 1.05 105 32 12 32 Pressure MPa 3.5 2.24 2.24 2.2 2.2 0.1 1.21.1 0.1 0.1 3.2 1.2 3.2 Vapor Fraction 0 1 1 1 1 1 1 1 1 1 0 0 0Enthalpy J/KMOL −2.72E+08 −8.24E+07 −5.96E+07 −1.56E+05 1.27E+07−3.64E+08 6.35E+06 5.13E+06 −1.29E+07 −2.69E+07 −2.85E+08 6.35E+06−2.85E+08 Average MW 18.02 18.94 18.94 28.05 28.05 28.84 28.84 28.3928.43 28.43 18.08 28.84 18.08 Note - based on iso-conditions for the gasturbine

The exemplified embodiment of the present invention is compared with theNatural Gas Fischer-Tropsch Technology report carried out by Bechtel Ltdfor the U.S DOE Pittsburgh Energy Technology Center (Reference—U.S.Department of Energy Pittsburgh Energy Technology Center—BaselineDesign/Economics for advanced Fischer Tropsch Technology Contract No.DE-AC22-91PC90027. Tropical Report VI—Natural Gas Fischer Tropsch CaseVolume II Plant Design and Aspen Process Simulation Model—by Bechtel LtdAugust 1996.)

Basis Invention Saving Synthesis gas kmol/h 59860 59860 productionNatural gas used MMSCFD 411.9 396  4% (Nm³/h) (4.51 × 10⁵) (4.33 × 10⁵)O₂ used (99.5% purity) MTD 11391 6791 40% (Kg/h) (4.75 × 10⁵) (2.83 ×10⁵) FT Gasoline produced Bbl/day 17030 17030 (m³/h) (112.8) (112.8) FTDiesel produced Bbl/day 26210 26210 (m³/h) (173.6) (173.6) Propaneproduced Bbl/day 1700 1700 (m³/h) (11.3) (11.3) Thermal Efficiency %56.94% 58.57% (LHV - Lower Heating Value)

The invention figures are based on non-iso conditions for the gasturbine performance. The Fischer Tropsch synthesis has been scaled fromthe basis case to give consistent results. The same natural gascomposition was also used to ensure the energy balances were alsoconsistent. Further, the computer simulation of the invention processincorporates a carbon dioxide recycle to the GHR (in order to make morehydrogen to balance the process) solely for comparative purposes. Thisrecycle step actually reduces the efficiency of the present invention.

In another embodiment of the present invention, a synthesis gas streamwith a hydrogen to carbon monoxide ratio of about 2:1 and a carbondioxide composition of about 5% is required for an F-T plant. The F-Tsynthesis produces pure carbon dioxide and fuel gas as a by-product. Forthis flowsheet, the carbon dioxide is fed to the GHR as part of the feedto achieve the required 2:1 hydrogen to carbon monoxide ratio in thesynthesis gas stream. The fuel gas has a high enough calorific value tobe used instead of natural gas in the gas turbine. The steam to carbonratio required is about 2.2:1 for this case so the excess steam producedin the HRSG is added to the fuel for the gas turbine. This conditionsthe fuel in the gas turbine and will help to reduce the NO_(x) emissionsfrom turbine. The other significant change is that there is no longerany need to shift carbon monoxide to hydrogen so the shift reactor isomitted from the flowsheet.

It will be appreciated that the invention is not restricted to thedetails described above with reference to the preferred embodiments butthat numerous modifications and variations can be made without departingfrom the scope of the invention as defined in the following claims.

What is claimed is:
 1. Apparatus for the production of synthesis gas,said apparatus comprising: a synthesis gas generation system forreacting hydrocarbon fuel gas with steam and/or oxygen gas to produce asynthesis gas product stream; compressing means for compressing anoxidant gas to produce compressed oxidant gas; combusting means forcombusting combustion fuel gas in the presence of at least a portion ofsaid compressed oxidant gas to produce combustion product gas; expandingmeans for expanding said combustion product gas to produce power andexpanded combustion product gas; heat exchange means for heating a firststeam stream against a stream of expanded combustion product gas toproduce a heated first steam stream; conduit means for supplying thestream of expanded combustion product gas from the expanding means tothe first heat exchange means; conduit means for supplying at least aportion of the heated first steam stream from the first heat exchangemeans to the synthesis gas generation system; an air separation unit(“ASU”); means for transferring at least a portion of the power producedby the expanding means to the ASU; and conduit means for supplying atleast a portion of the oxygen gas from the ASU to the synthesis gasgeneration system.
 2. The apparatus according to claim 1 wherein thesynthesis gas generation system comprises in combination: a partialoxidation reactor (“POX”) in which hydrocarbon fuel gas is partiallyoxidized in the presence of oxygen gas to produce a first intermediatesynthesis gas product; and a gas heated reformer (“GHR”) in whichhydrocarbon fuel gas is reformed with steam to produce a secondintermediate synthesis gas product which is combined with the firstintermediate synthesis gas product to form the synthesis gas productstream.
 3. The apparatus according to claim 1, wherein the synthesis gasgeneration system comprises a GHR in which hydrocarbon fuel gas isreformed with steam to produce the synthesis gas product stream.
 4. Theapparatus according to claim 1 wherein the synthesis gas generationsystem comprises an autothermal reformer (“ATR”) in which hydrocarbonfuel gas, steam and oxygen gas are reacted to produce the synthesis gasproduct stream.
 5. The apparatus according to claim 1 furthercomprising: heat exchange means for heating water by heat exchangeagainst the expanded combustion product gas stream to produce a heatedsecond steam stream; further heat exchange means for heating an oxygengas stream by heat exchange against the heated second steam stream toproduce a heated oxygen gas stream; and conduit means for feeding atleast a portion of the heated oxygen gas stream to the synthesis gasgeneration system.
 6. The apparatus according to claim 1 furthercomprising; heat exchange means for heating water by heat exchangeagainst the expanded combustion product gas stream to produce a heatedthird steam stream; and conduit means for feeding the heated third steamstream to the combustion means.
 7. The apparatus according to claim 1further comprising; heat exchange means for heating a compressednitrogen stream by heat exchange against the expanded combustion productgas stream to provide a heated compressed nitrogen stream; and conduitmeans for feeding the heated compressed nitrogen stream to thecombustion means.
 8. The apparatus according to claim 7 furthercomprising a compressor for producing said compressed nitrogen stream bycompressing a stream of nitrogen produced in the ASU.
 9. The apparatusaccording to claim 1 further comprising a synfuel generation system forprocessing the synthesis gas product stream or a stream derivedtherefrom to produce a synfuel.
 10. The apparatus according to claim 9wherein the synfuel generation system comprises a Fischer-Tropsch(“F-T”) reactor for production of a mixture of high molecular weighthydrocarbon products.
 11. The apparatus according to claim 10 whereincombustible off-gases are generated in the F-T reactor, said apparatusfurther comprising conduit means for introducing at least a portion ofsaid combustible off-gases to the combustion means.
 12. The apparatusaccording to claim 10 wherein combustible off-gasses are generated inthe F-T reactor, said apparatus further comprising: means for combininga stream of at least a portion of said combustible off-gases or a streamderived therefrom with a stream of hydrocarbon fuel gas to produce acombined stream; and conduit means for introducing said combined streamto the combustion means.
 13. The apparatus as claimed in claim 9 whereinthe synfuel generation system comprises a reactor provided with a carbonmonoxide hydrogenation catalyst for the production of methanol.
 14. Theapparatus according to claim 13 wherein a purge gas stream comprisingunreacted synthesis gas and inert gas is removed from the reactor, saidapparatus further comprising conduit means for feeding at least aportion of the purge gas stream or a stream derived therefrom as fuel tothe combustion means.
 15. The apparatus according to claim 13 wherein apurge gas stream comprising unreacted synthesis gas and inert gas isremoved from the reactor, said apparatus further comprising; means forcombining at least a portion of the purge gas stream or a stream derivedtherefrom from the reactor with hydrocarbon fuel gas to produce acombined purge gas stream; and conduit means for feeding at least aportion of the combined purge gas stream to the synthesis generationsystem.
 16. The apparatus according to claim 1 wherein the compressingmeans, the combusting means and the expanding means are stages of a gasturbine.
 17. Apparatus for the production of synthesis gas, saidapparatus comprising: a POX in which hydrocarbon fuel gas is partiallyoxidized in the presence of oxygen gas to produce a first intermediatesynthesis gas product; and a GHR in combination with the POX in whichhydrocarbon fuel gas is reformed with steam to produce a secondintermediate synthesis gas product which is combined with the firstintermediate synthesis gas product to form a synthesis gas productstream; a gas turbine in which an oxidant gas is compressed to producecompressed oxidant gas, a combustion fuel gas is combusted in thepresence of at least a portion of said compressed oxidant gas to producecombustion product gas and said combustion product gas is expanded toproduce power and expanded combustion product gas; heat exchange meansfor heating a first steam stream against a stream of expanded combustionproduct gas to produce a heated first steam stream; conduit means forsupplying the stream of expanded combustion product gas from theexpanding means to the first heat exchange means; conduit means forsupplying at least a portion of the heated first steam stream from thefirst heat exchange means to the synthesis gas generation system; an airseparation unit (“ASU”); means for transferring at least a portion ofthe power produced by the gas turbine to the ASU; and conduit means forsupplying at least a portion of the oxygen gas from the ASU to thesynthesis gas generation system.